Abstract The paper presents the design, implementation and results of a microbial single-well stimulation test performed at the Diadema field in Argentina. The purpose of the test was to achieve increased production by injecting a microbial formulation and nutrients, and to gain experience with this procedure under actual field conditions. Two out of five treated wells showed excellent oil production response to the microbial stimulation.
The results suggest that a microbial-enhanced waterflood could be implemented successfully at the Diadema field
Introduction A microbial single-well stimulation field test was performed at the Diadema field in Argentina between October 1992 and March 1993 by the Argentine companies CAPSA (field owner) and APAC-Flow Technologies (microbial supply and injection) with the technical support of the National Institute for Petroleum and Energy Research (NIPER), Bartlesville, Oklahoma, USA.
The purpose of the project was to achieve increased production by injecting a microbial formulation and nutrients in five producer wells, and to test the viability of this procedure in actual field conditions. Further, the test would allow preliminary conclusions towards implementing in the future a microbial enhanced waterflood.
MICROBIAL ENHANCED OIL RECOVERY (MEOR)
Microbial methods for improving oil recovery are potentially cost effective and particularly well suited for today's economic climate, since they require little capital expenditure and are easily implemented in the field. However, careful design and sound engineering practice is a requisite for a successful microbial treatment. Microbial formulations can be used in a variety of methods including single-well stimulation treatments, permeability modification treatments and microbial enhanced waterflooding.
The concept of the use of microorganisms to recover oil from depleted reservoirs is not new. Beckmann first suggested microbial techniques for enhancing oil production. Field and laboratory research have been performed and patents have been granted for this technology since the late 1940s. Several literature reviews on MEOR have been published. Recent applications of microbial formulations to enhancing oil production at an ongoing waterflood in the USA include NIPER's activities at the Mink Unit and Phoenix Field Pilots, the latter comprising 19 injection wells and monitoring of 47 production wells. Art increase in oil production of 19.6% by May 1993 has been reported for the latter.
Laboratory research has demonstrated that the products from microbial fermentation of nutrients can change the interfacial properties between oil and water and increase wellhead pressure in single-well injections. Some microbial species can also improve oil production by helping to remove suspended debris and paraffins near the wellbore region.
Microorganisms most commonly used for MEOR field processes produce surfactants, gases, alcohols, acids and solvents. The microbial formulation can be designed to improve microscopic oil displacement efficiency for a particular field.
For the Diadema project, a microbial formulation was designed to produce gas, acids, alcohols and surfactant.
FIELD DATA The Diadema oil field belongs to the San Jorge Gulf basin and is located in the Province of Chubut in the southern part of Argentina (Fig. 1). Oil production as of September 1993 is 883 m3 per day from 202 producing wells. Accumulated oil production is 23.5 millions m3, with 19.1 million m3 produced from complex I and II. The formation selected for this pilot test is the Upper Garnet Zone (U.G.Z.) of complex II.
A comparison of the recommended range of field characteristics for microbial application and those of U.G.Z. is shown in Table 1, as well as relevant field data. The current project's characteristics are typical of reservoirs that are present in most of the fields of the San Jorge basin.